Mars Hill, in Flagstaff, Arizona, is famous for two things: Percival Lowell's observations of Mars starting in the late 19th century, and Clyde Tombaugh's discovery of Pluto in 1930 (still a planet despite what unscientific political decisions the IAU might make). It is a classic place in a nice town with volcanoes and two brewpubs! Lowell was a rich guy (the town of Lowell, MA is named after his family) who wanted to observe, so he had the big 24-inch Alvan Clark refractor and its dome made for him in 1894. Long focal length refractors are great for planetary observing, and he used it to study Mars and its "canals", which he mapped (see globes). We know now that some of them are real geologic features, others just a product of observing at the cutting edge of Victorian technology before space telescopes and rovers. Around 1912-7, it was used by V.M. Slipher to record the first evidence of an expanding universe. The scope was also used by Apollo astronauts in the 1960s to study their Moon landing sites. Below are views of the dome, the looooooooooooooong refractor (unlike the boxy reflectors made today, which are hard to photograph because there is barely any room in their domes, this dome has plenty of room, but the scope is too damn long!), and the famous observing chair used by Lowell. Note the car tires that the whole dome rests on, these were added in the 1950s and like everything else here, still work fine today! The observatory is still a private facility open to the public and supported by tour fees and donations. I believe you can book time on the Clark if you want.
Below is the dome and photographic telescope specially made for Clyde Tombaugh to survey in the late 1920s for planets beyond Neptune. It was tedious work, but he succeeded! A whole family of small planets (spherical non-stellar objects) in this region of the solar system are still being found, some are larger than Pluto. The scope is no longer used, just preserved as a historical artifact.
Below is the rotunda for the offices, which houses some artifacts, including Lowell's Mars globes, and the blink comparator used by Tombaugh. Inside the comparator are the Pluto discovery images and you can actually use it to "discover" Pluto again....it ain't easy! Thank goodness there are computers for that today....still, very cool!